Centrifuge rotor assembly

ABSTRACT

An improved centrifuge rotor assembly having a plurality of tube-receiving sleeves pivotally mounted about the periphery of the rotor, each sleeve being associated with a spring member. Each spring has a pair of flexible fingers, one of which is disposed within the tube-receiving sleeve for frictionally holding a centrifuge tube within that sleeve. The other finger bears against the rotor to urge the sleeve into a vertical position, thereby cushioning pivotal movement of the sleeve (and the tube supported therein) under the influence of centrifugal force as the rotor accelerates, and holding such sleeve in a position generally parallel with the axis of the rotor when the rotor is stationary.

United States Patent [191 Guerrero [451 Jan. 22, 1974 [73] Assignee: American Hospital Supply Corporation, Evanston, Ill.

22 Filed: Sept. 7, 1972 21 Appl.No.: 287,095

Primary ExaminerGeorge H. Krizmanich Attorney, Agent, or FirmDawson, Tilton, Fallon &

Lungmus [5 7 ABSTRACT An improved centrifuge rotor assembly having a plurality of tube-receiving sleeves pivotally mounted about the periphery of the rotor, each sleeve being associated with a spring member. Each spring has a pair of flexible fingers, one of which is disposed within the tube-receiving sleeve for frictionally holding a centrifuge tube within that sleeve. The other finger bears against the rotor to urge the sleeve into a vertical position, thereby cushioning pivotal movement of the sleeve (and the tube supported therein) under the influence of centrifugal force as the rotor accelerates, and holding such sleeve in a position generally parallel with the axis of the rotor when the rotor is stationary.

13 Claims, 5 Drawing Figures PATENTED JAN 2 2 I974 sum 1 BF 2 FIG?) FIGI CENTRIFUGE ROTOR ASSEMBLY BACKGROUND The testing of blood samples in a typical clinical laboratory generally involves a large number of such samples which must be given specific tests as efficiently as possible. Multiple tube centrifuges have been developed in an effort to meet such needs; however, for the most part such centrifuges have been relatively complex in construction and have been deficient in one or more important respects. Thus, in some cases the pivotal action of the holders or sleeves for the centrifuge tubes has been insufficiently controlled, thereby exposing the tubes to abrupt movement which could result in re-suspending the precipitate and which, in severe cases, might cause breakage of the frangible glass tubes and the associated parts of the centrifuge.

Another common deficiency of prior centrifuges lies in the fact that complete or partial emptying of the tubes can be accomplished only by the time-consuming operation of individually removing the tubes from the rotor and then pouring off the contents of each tube. In an effort to increase speed and efficiency, some technicians have fitted elastic bands about the multiple tubes supported by a rotor, thereby permitting all tubes to be emptied simultaneously. While the constricting effect of an elastic band might normally be effective in holding the tubes together, any failure in such a makeshift restraint would necessarily increase the likelihood of tube breakage and might present serious danger to the technician.

SUMMARY The present invention is concerned with an improved centrifuge rotor assembly and, more particularly, to a rotor equipped with dual-functioning spring members for the centrifuge tubes and sleeves.

In general, the construction of the present invention comprises a centrifuge rotor with a plurality of sleeves spaced circumferentially and uniformly about the periphery thereof. Each sleeve has a vertical rest position and is pivotally mounted, with its pivot line extending tangentially of the rotor and above the mid-point of the sleeve, to pivot outwardly under the influence of centrifugal force. A tube spring is associated with each sleeve. Each spring has a hub, an upwardly and downwardly curved hook-shaped finger, and a second finger projecting inwardly towards the axis of the rotor. The depending free end portion of the hook-shaped finger projects into the open upper end of a centrifuge sleeve and bears firmly against the outer side surface of a centrifuge tube to retain the tube by frictional force within its sleeve or holder. The frictional force is sufficient to hold the tube in its sleeve even when the rotor is completely inverted; however, it is not great enough to interfere with manual insertion and removal of the tube.

The hub of each spring member is pivotally attached to the rotor with its pivot axis preferably coincident with the pivot axis of the sleeve or holder associated therewith. In a preferred embodiment, the hub is fixed to the sleeve for simultaneous pivoting therewith. Therefore, as the sleeve (and the centrifuge tube contained therein) pivots outwardly under the influence of centrifugal force, the hub of the spring member also pivots to produce deformation of the horizontal second finger or tongue of the spring member. The flexible sec- 0nd finger has its free end portion slidably received within a radially-extending channel adjacent the axis of the rotor and, as the hub of the spring member pivots in response to centrifugal force, the normally straight second finger flexes to accommodate and cushion such pivotal movement, the end portion of such finger sliding to a limited extent within its channel as such deformation occurs.

THE DRAWINGS FIG. 1 is a perspective view of a centrifuge rotor assembly embodying the present invention;

FIG. 2 is a perspective view of a spring member for such assembly;

FIG. 3 is an enlarged fragmentary vertical sectional view taken along line 3-3 of FIG. 1 and showing the sleeve and centrifuge tube in a normal vertical rest position;

FIG. 4 is an enlarged fragmentary sectional view similar to FIG. 3 but showing the sleeve and centrifuge tube pivoted outwardly under the influence of centrifugal force;

FIG. 5 is an enlarged fragmentary vertical sectional view similar to FIG. 3 but showing the rotor assembly in an inverted position.

DESCRIPTION Referring to FIG. 1, numeral 10 generally designates a centrifuge rotor assembly comprising a disk-shaped rotor 11 having a hub 12 adapted to fit slidably upon the vertical shaft of a centrifuge (not shown). The assembly is removable as a unit from the upstanding centrifuge shaft and suitable means, such as a spline adapted to be received within channel 13 of the hub, lock the shaft and hub against independent relative rotation without at the same time preventing separation of the parts. Since the centrifuge and its drive shaft may be entirely conventional and constitute no part of the present invention, further description of that structure and its operation is believed unnecessary herein.

A plurality of tube holders 14 are spaced uniformly about the periphery of the rotor and are provided with sleeve portions 15 of generally cylindrical configuration. As shown most clearly in FIG. 3, the sleeves are open topped but are closed at their bottom ends. Standard glass centrifuge tubes 16 are received within the sleeves, the outside diameter of each tube being substantially less than the internal diameter of the sleeve.

Each tube holder is also provided with a connecting portion 17 which faces inwardly towards the axis 18 of the rotor and which is received within a recess 19 extending inwardly from the rotors periphery. Tangentially extending pivot pins 20 support each holder or sleeve for pivotal movement between the normally vertical position illustrated in FIG. 3 (wherein the sleeve is generally parallel with the axis 18 of the rotor) and an inclined position illustrated in FIG. 4 (wherein the sleeve slopes upwardly and inwardly towards the rotors axis). FIG. 4 illustrates the relationship of parts when the centrifuge is in operation. To produce the outward swinging action illustrated, it is believed apparent that the horizontal axis of pivot 20 must be disposed above the longitudinal mid-point (or balance center) of the tube-holder combination.

FIG. 2 illustrates a unitary spring member 21 having a hub 22, a hook-shaped finger 23, and a second finger or tongue 24. The hub is provided with a horizontal opening for receiving pivot pin 25, the pivot axes for the hub and tube holder 14 therefore being coextensive. It will be observed that the hub is generally noncircular in configuration and engages the walls of connecting portion 17 so that the hub and tube holder 14 are locked against independent pivotal movement.

Finger 23 extends upwardly from the hub, then curves outwardly, and then extends downwardly, terminating in a depending end portion 230 disposed within the cavity of sleeve 15. As shown in FIGS. 1 and 3, the sleeve is provided with an opening 26 through which finger 23 projects.

As previously indicated, the internal diameter of sleeve 15 is substantially larger than the outside diameter of tube 16. However, the depending end portion 230 of finger 23 projects well into the interior of the sleeve for frictional engagement with tube 16. Specifically, when finger 23 is untensioned, end portion 23a slopes downwardly and outwardly into the space which would normally be occupied by a centrifuge tube 16, as

illustrated by broken lines in FIG. 3. When a tube 16 is inserted into sleeve 15, direct engagement between the tube and finger portion 23a causes the finger to flex into the condition illustrated by solid lines in FIG. 3. The tube, in turn, is urged outwardly into snug frictional contact with the outer inside surface of sleeve 15. The frictional contact between tube 16 and the opposing surfaces of finger portion 23a and sleeve 15 is sufficient to hold the tube in place even when the entire rotor is inverted (FIG. 5). However, the frictional resistance is not sufficient to prevent inward and outward sliding movement of tube 16 when manual insertion or withdrawal is desired. The inverted U-shaped configuration of finger 23 not only provides for proper flexing action but also, because of the arcuate convex configuration of the fingers outer surface, tends to guide rather than obstruct insertion of a centrifuge tube 16 into sleeve 15.

Tongue or finger 24 extends radially inwardly beneath horizontal wall 11a of the rotor. The end portion 24a of the tongue is slidably received within a channel or recess 27 which restrains that portion against vertical movement without preventing limited axial sliding movement. It will be observed from FIGS. 3 and 4 that a space 28 is provided by the rotor beneath all but the end portion 24a of tongue 24; therefore, when holder 14 pivots outwardly (FIG. 4), the tongue or strap is free to flex into space 28. Because of the flexibility or resilience of tongue 24, such distortion is resisted, thereby cushioning holder 14 and its contents against abrupt movement between its vertical rest position and its inclined operating position. As the holder swings outwardly, end portion 24a of tongue or finger 24 slides radially outwardly to a limited extent within recess 27 of the rotor.

It. is believed apparent that the spring member not only cushions or yieldably restrains outward pivoting movement of the holder but also serves as a return spring for guiding the holder into the vertical position of FIG. 3 and for maintaining the holder in that position. Thus, the entire rotor may be removed from its drive shaft or spindle and may be moved about without danger that the tube holders will swing or flop about on their individual pivots. Since the spring members 24 urge the holders into the vertical positions illustrated in FIG. 1, the entire assembly may be removed from the centrifuge and placed on a flat surface, the bottom ends of sleeves l5 resting on that surface. Furthermore, the entire assembly may be inverted as shown in FIG. 5 for the purpose of draining fluid from all of the tubes simultaneously, the spring members acting to maintain all of the sleeves and tubes in parallel relation to the axis 18 of the rotor.

Spring member 21 may be formed of any suitable material having the necessary characteristics of flexibility and durability. While the member may be formed of metal, it has been found that tough flexible plastic materials are particularly suitable because they permit manufacture of the member as an integral molded piece and because such material promotes smooth nonabrasive coaction between the spring member, tube 16, and rotor 12.

While in the foregoing an embodiment of the invention has been disclosed in considerable detail for purposes of illustration, it will be understood by those skilled in the art that many of these details may be varied considerably without departing from the spirit and scope of the invention.

I claim:

1. A spring member for pivoting centrifuge tube holders, comprising a hub having a horizontal axis, a spring finger extending upwardly from said hub and then downwardly with respect thereto, said finger terminating in a downwardly projecting free end portion disposed on one side of said hub, said free end portion being capable of flexing towards and away from said hub and adapted to bear frictionally against the outer surface of a centrifuge tube, and a second spring finger projecting generally horizontally from the side of said hub opposite said one side, said second finger being generally straight when in an unflexed condition and having a free end adapted to be restrained for controlling the extent of pivotal movement of said hub about said axis.

2. The structure of claim 1 in which said fingers are formed integrally with said hub.

3. The structure of claim 2 in which said spring member is formed integrally of flexible plastic material.

4. The structure of claim 1 in which said firstmentioned finger is of generally inverted U-shaped configuration.

5. The structure of claim 1 in which said second spring finger extends in a generally horizontal direction.

6. A centrifuge rotor assembly comprising a rotor adapted for rotation about a vertical axis, a centrifuge tube holder mounted upon said rotor adjacent the periphery thereof, said holder being mounted on said rotor for pivotal movement about a tangentiallyextending pivot axis and having a sleeve portion defining an upwardly-opening cavity for receiving a centrifuge tube, and a spring member mounted upon said rotor and having a spring finger projecting downwardly into said sleeve for frictionally engaging a centrifuge tube-disposed therein, said spring member having a hub portion fixed to said holder for pivotal movement along with said holder, said spring member also having a second spring finger projecting inwardly towards the axis of said rotor, said second finger having an end portion engaging said rotor and being restrained by said rotor to urge said holder into a normal position wherein the axis of said sleeve portion is generally parallel with the axis of said rotor, said second finger also having an elongated intermediate portion adapted to flex downwardly beneath said rotor when said holder is pivoted away from its normal position, and said rotor providing a space to accommodate said downward flexure of said intermediate portion.

7. The structure of claim 6 in which said spring fingers of said member are integrally molded of plastic material.

8. A centrifuge rotor assembly comprising a rotor adapted for rotation about a vertical axis of centrifugation, a plurality of centrifuge tube holders spaced uniformly about the periphery of said rotor, each holder having a sleeve defining an upwardly-opening cavity and being mounted upon said rotor for pivotal movement about a tangentially-extending pivot axis between having an end portion received within one of said channels in said rotor for limited sliding movement therein as said finger flexes during pivotal movement of the holder associated therewith, said rotor providing a space to accommodate such flexure of each said finger.

9. The structure of claim 8 in which each said finger is normally straight and extends inwardly towards said axis of centrifugation, each said finger having an intermediate portion adapted to flex downwardly as the holder associated therewith is pivoted into its inclined position.

10. The structure of claim 8 in which said spring members are formed of flexible plastic material.

11. The structure of claim 10 in which each of said spring members is provided with a second spring finger having an end portion projecting downwardly into said sleeve for frictional engagement with a centrifuge tube adapted to be received therein.

12. The structure of claim 11 in which said second finger is of generally inverted U-shaped configuration.

13. The structure of claim 11 in which said spring fingers are formed integrally with a hub portion, each said hub portion being fixed to the holder associated therewith. 

1. A spring member for pivoting centrifuge tube holders, comprising a hub having a horizontal axis, a spring finger extending upwardly from said hub and then downwardly with respect thereto, said finger terminating in a downwardly projecting free end portion disposed on one side of said hub, said free end portion being capable of flexing towards and away from said hub and adapted to bear frictionally against the outer surface of a centrifuge tube, and a second spring finger projecting generally horizontally from the side of said hub opposite said one side, said second finger being generally straight when in an unflexed condition and having a free end adapted to be restrained for controlling the extent of pivotal movement of said hub about said axis.
 2. The structure of claim 1 in which said fingers are formed integrally with said hub.
 3. The structure of claim 2 in which said spring member is formed integrally of flexible plastic material.
 4. The structure of claim 1 in which said first-mentioned finger is of generally inverted U-shaped configuration.
 5. The structure of claim 1 in which said second spring finger extends in a generally horizontal direction.
 6. A centrifuge rotor assembly comprising a rotor adapted for rotation about a vertical axis, a centrifuge tube holder mounted upon said rotor adjacent the periphery thereof, said holder being mounted on said rotor for pivotal movement about a tangentially-extending pivot axis and having a sleeve portion defining an upwardly-opening cavity for receiving a centrifuge tube, and a spring member mounted upon said rotor and having a spring finger projecting downwardly into said sleeve for frictionally engaging a centrifuge tube disposed therein, said spring member having a hub portion fixed to said holder for pivotal movement along with said holder, said spring member also having a second spring finger projecting inwardly towards the axis of said rotor, said second finger having an end portion engaging said rotor and being restrained by said rotor to urge said holder into a normal position wherein the axis of said sleeve portion is generally parallel with the axis of said rotor, said second finger also having an elongated intermediate portion adapted to flex downwardly beneath said rotor when said holder is pivoted away from its normal position, and said rotor providing a space to accommodate said downward flexure of said intermediate portion.
 7. The structure of claim 6 in which said spring fingers of said member are integrally molded of plastic material.
 8. A centrifuge rotor assembly comprising a rotor adapted for rotation about a vertical axis of centrifugation, a plurality of centrifuge tube holders spaced uniformly about the periphery of said rotor, each holder having a sleeve defining an upwardly-opening cavity and being mounted upon said rotor for pivotal movement about a tangentially-extending pivot axis between a generally vertical position and an inclined position, and a plurality of spring members carried by said holders and having elongated flexible fingers terminally engaging said rotor for urging said holders into their generally vertical positions, said spring members having hub portions with pivot axes coextensive with the pivot axes of said holders, said rotor being provided with a plurality of radially-extending channels, each finger having an end portion received within one of said channels in said rotor for limited sliding movement therein as said finger flexes during pivotal movement of the holder associated therewith, said rotor providing a space to accommodate Such flexure of each said finger.
 9. The structure of claim 8 in which each said finger is normally straight and extends inwardly towards said axis of centrifugation, each said finger having an intermediate portion adapted to flex downwardly as the holder associated therewith is pivoted into its inclined position.
 10. The structure of claim 8 in which said spring members are formed of flexible plastic material.
 11. The structure of claim 10 in which each of said spring members is provided with a second spring finger having an end portion projecting downwardly into said sleeve for frictional engagement with a centrifuge tube adapted to be received therein.
 12. The structure of claim 11 in which said second finger is of generally inverted U-shaped configuration.
 13. The structure of claim 11 in which said spring fingers are formed integrally with a hub portion, each said hub portion being fixed to the holder associated therewith. 